In this study, a new topology, using AC choppers is proposed for reactive power compensation in 25 kV/50 Hz railway networks. The low losses of these converters compared to other solutions such as voltage-sourced inverters-based STATCOMs, makes this approach attractive for high-power, single-phase systems such as railway networks. A possible solution based on the controlled impedance concept working in boost mode is proposed and applied to a substation in the French rail network. Design method presented end simulation results which confirm the performance of this low-cost and low-loss solution. Finally, the experimental results achieved on a 1.2 MVAR prototype are presented. View full abstract»

Permanent-magnet synchronous motors (PMSM) are capable of providing high torque-to-current ratios, high power-to-weight ratios, high efficiency and robustness. Owing to these advantages, PMSM are widely used in modern variable speed AC drives, especially in electric vehicle (EV) and hybrid EV applications. In this study, a novel PMSM drive system with a bidirectional Z-source inverter (ZSI) is proposed and tested. By introducing ZSI to the drive system, the DC-link voltage is controllable so that PMSM can operate at high speed without field weakening. The operating principle and modulation method of ZSI are described in this study. After presenting the constraints of the motor maximum line current amplitude and maximum available voltage, a modified vector controlled scheme of PMSM drive is developed by considering voltage boosting. Finally, the feasibility and effectiveness of the proposed system are verified by several simulation and experiment results. View full abstract»

The nature of transport and energy use is radically changing along with the upward trend of electric vehicles (EVs). This poses a challenge for the existing electricity distribution infrastructure. Key questions are: what efforts are required to guarantee that the network infrastructure has sufficient capability to deliver energy and power to the customers, and how does this development affect the network value and distribution fees? In this study, this challenge is approached from the economic perspective of an electricity distribution company. In this study, a generic model to analyse the network effects of EVs is presented. One significant result is that depending on the EV charging methods, the power demand (peak load) may increase dramatically or remain almost at the present level. Correspondingly, the required network reinforcements and distribution fees can be tens of percents lower than today or they can be higher, depending on how much intelligence is integrated into the charging process. View full abstract»

In this study, an analysis of the use of the DC grid of electric vehicles as a communication channel for broadband power line communications (PLC) is presented. A measurement campaign of channel frequency responses is reported for different access points inside the vehicle, and also between the vehicle and the external grid during battery charging. The noise produced by the motor drive and the AC/DC converter is measured and characterised in time and frequency domain. A wavelet-based method is used to create a simulation model of the channel frequency responses, which is used together with the measured noise andis used to perform a performance analysis of the channels by calculating the symbol error rate using a multicarrier communication scheme. From the analysis, the authors conclude that a broadband PLC onboard electric vehicle is feasible if advanced PLC schemes are used. View full abstract»

This study presents a new equivalent lithium-ion (Li-ion) battery model for online energy management system. It has an equilibrium potential E and an equivalent internal resistance Rint. The equilibrium potential E is expressed as a function of state-of-charge (SOC), current and temperature. The equivalent internal resistance Rint includes R1 and R2. R1 is defined as the resistance, which can be formulated by the discharging current and temperature. R2 is defined as the resistance which is because of the change of temperature. The adaptive extended Kalman filter is employed to implement the online energy management system based on the proposed Li-ion battery model. The SOC is considered as the state variable for the charging or discharging process of the Li-ion battery. The covariance parameters of the processing noise and observation errors are updated adaptively. The SOC of the Li-ion battery can be predicted by the online measured voltage and current in the online energy management system. The effectiveness and robustness of the proposed Li-ion battery model is validated. Experimental results show that the estimated SOC is accurate for various operating conditions. A comparison between the proposed method and other SOC estimation methods is also shown in the experimental results and analysis section. View full abstract»

Power electronics are becoming increasingly important in modern ship board power systems. They are used for development and implementation of controls and to interface different electrical modules such as loads, batteries and generators that produce, store or consume energy. Power electronic systems are suitable for control because they provide fast operation in the range of microseconds. However, fast control operations can also add complexity to the system. Unintended complex dynamics can arise if the system (inertia) is unable to adapt to the control actions. This article studies the complexity and emergent phenomena that may develop in a ship board power system because of the power electronic components, coupling between these components, as well as feedback mechanisms such as control loops and those of human and environmental origin. A statistical complexity measure, referred to as structural complexity, is used to quantify the degree of complexity that arises during the system evolution. This metric of complexity is computed using permutation entropy and ordinal patterns. A modified procedure for structural complexity called multivariable structural complexity is developed to compute the system wide complexity. This multivariable structural complexity is also used to assist the modelling process and the decision of the best model candidate that captures observed aspects of complexity from the system data history. Various case studies on complexity quantification are conducted on simulated data from a noise coupled buck converter, two parallel connected buck converters and an electric ship board power system. View full abstract»